The present invention pertains generally to electroactive materials and in particular to organic polymeric conductive materials.
TCNQ compositions are useful as conductors in both pure form and as an ingredient in compositions. However, pure TNCQ compounds are crystalline in nature and do not have desirable structural properties. When TCNQ is used an ingredient in a composition, an improvement in structural properties may be achieved. However, this improvement is generally at the expense of the desired conductivity.
In order to obtain a substance with the desirable electrical qualities of TCNQ and also improved structural properties, various compositions of TCNQ with polymers have been developed. However, these prior art compositions have had one or more of the following shortcomings: (1) they could be produced only in film, as opposed to bulk, moldable form; (2) the electrical properties of the TCNQ were adversely affected when combined with the polymer; (3) the composition was not stable against heat or atmospheric degradation.
For example, U.S. Pat. No. 3,966,987 describes a conductive TCNQ composition used to form the plates of a capacitor. But this composition could be used only in film, as opposed to moldable form. Other examples of film TCNQ compositions are found in U.S. Pat. Nos. 4,202,799; 3,828,008, and 3,835,102.
A moldable conductive polymer invention is disclosed in U.S. Pat. No. 3,448,177. However, the Patentee warns that the substances claimed are very susceptable to atmospheric degradation. Futhermore, the conductivities claimed are low compared to those of the crystalline TCNQ salt. Furthermore, the cation associated with the TCNQ radical-anion is built into the structural polymer. This limits the choice of cations to those which can be incorporated into the polymer itself. Furthermore, the method described for preparing the composition involves heating the TCNQ while it is in contact with the solvent. It has been discovered by the applicant that such heating is harmful because it causes side reactions that degrade the conductivity of TCNQ.
In some cases, moldable TCNQ compositions have been claimed as dielectric material in capacitors. For example, a composition of TCNQ and polymer is disclosed in U.S. Pat. No. 3,679,944 as a dielectric material, as opposed to a conductor. However, the TCNQ compositions in these cases suffer from problem (2) described above, in that normally conductive TCNQ is caused to be non-conductive in the composition. This is accomplished by "dispersing" the TCNQ throughout the polymer bulk so that the typical electrical conductivity of TCNQ cannot manifest itself. The polymer insulates the conductive TCNQ molecules from one another. If the goal is to make a dielectric i.e., an insulating material, this is desirable. If the goal is to make a conductive polymeric material, this change in the normal conductivity of the TCNQ is exactly the opposite of what is needed.